Method for processing large-size postal objects in a sorting installation

ABSTRACT

The method of processing postal objects of large size in order to read automatically a postal address (AD) on each object consists in acquiring a digital image of each object at a certain level of resolution; in detecting in the image one or more zones of interest (ZI) apparently containing a postal address; in performing automatic address recognition on each zone of interest in order to extract a postal address (AD) of the object, and in the event of the automatic address recogition failing, in displaying each zone of interest (ZI) on a screen so that a video-coding operator can read the postal address (AD) of the object. Each zone of interest (ZI) is displayed on the screen on a screen context background (F) that is representative of the object but at a level of resolution that is lower than the level of resolution of the digital image and the zone of interest. In this way, the video-coding operator has an overall view of the detected zones of interest, thus making it easier to read the postal address of the object.

The invention relates to a method of processing postal objects, inparticular packets, for the purpose of automatically reading a postaladdress on each object, the method including a step of assistance bymeans of video-coding, consisting for each object in performing thefollowing steps:

a) acquiring a digital image of the object at a certain level ofresolution;

b) detecting in said digital image of the object one or more zones ofinterest of the image each apparently containing a postal address;

c) applying an automatic address recognition algorithm to each zone ofinterest detected in the image of the object in order to extract apostal address of said object; and

in which in the event of the step of automatic address recognitionfailing, each zone of interest is displayed on a screen of avideo-coding station in order to enable an operator to performsemi-automatic processing to read the postal address of said object.

Such a method is used more particularly in postal sorting where, on thebasis of automatically reading the destination postal address, eachpacket is delivered on exit to a bin corresponding to its destination.More specifically, the system for processing, managing, and controllingsuch an installation is generally computerized in such a manner thatidentifying a postal address corresponds to the computer systemacquiring part or all of said postal address. In such a method, thepostal address to be identified is generally the destination address ofthe packet.

A destination address can be identified by recognizing the addressautomatically, providing the address is easily readable, bysemi-automatic processing using a video-coding operator if the addressis fairly readable, and by manual processing if the address is difficultto read. Such identification generally comprises acquiring an image ofthe packet at a particular level of resolution referred to as “high”resolution; detecting one or more zones of interest in said image, saidzones of interest apparently containing the destination address; andattempting to recognize an address automatically in each zone ofinterest in order to identify the destination address that appears onthe packet. If automatic address recognition fails, then each zone ofinterest is displayed on a screen of a video-coding station so that avideo-coding operator can assist in identifying the destination address.In the most unfavorable circumstances, where the video-coding operatordoes not manage to identify the destination address, the operator canspecify a zone of interest in which to make a new attempt at recognizingan address automatically, or can cause the packet to be delivered to aspecial outlet bin so that a video-coding operator can identify thedestination address by reading it directly from the packet.

In general, each zone of interest is displayed on its own, and that doesnot always give the video-coding operator enough information to be ableto identify the destination address. In particular, the position of eachzone of interest relative to the packet can constitute part of theinformation needed, for example in order to distinguish between thedestination address and the sender's address.

The object of the invention is to remedy those drawbacks.

To this end, the invention provides a method of processing postalobjects, in particular packets, in order to read a postal addressautomatically on each object, the method including a step of assistanceby video-coding, and consisting for each object in performing thefollowing steps:

a) acquiring a digital image of the object at a certain level ofresolution;

b) detecting in said digital image of the object one or more zones ofinterest of the image each apparently containing a postal address;

c) applying an automatic address recognition algorithm to each zone ofinterest detected in the image of the object in order to extract apostal address of said object; and

in which in the event of the step of automatic address recognitionfailing, each zone of interest is displayed on a screen of avideo-coding station in order to enable an operator to performsemi-automatic processing to read the postal address of said object, themethod being characterized in that in the event of the step of automaticaddress recognition failing, each zone of interest is displayed on thescreen on a screen context background representative of said digitalimage of the object but at a level of resolution that is lower than saidcertain level of resolution of the digital image.

Such a method shows the relative position of each zone of interest onthe packet, thus providing considerable additional information to makeit easier for a video-coding operator to identify the destinationaddress on the packet.

In a particular implementation of the invention, in which all of thezones of interest detected in a digital image of an object are displayedtogether on said screen context background in the event of the automaticaddress recognition step failing, a method is obtained in which thevideo-coding operator can distinguish directly between a destinationpostal address and a sender's postal address by displaying the relativepositions of said addresses on the packet.

In another particular implementation of the method of the invention, inwhich each zone of interest is displayed on the screen at anintermediate level of resolution higher than the level of resolution forthe screen context background and lower than the level of resolution forthe digital image of the object, a method is obtained in which theamount of computer data transmitted to the video-coding station isreduced, so that the time required to transmit said data is compatiblewith the throughput rate.

The invention is described below in detail and with reference to theaccompanying drawings, which show an implementation by way ofnon-limiting example.

FIG. 1 is a diagrammatic view of an image displayed on the screen of avideo-coding station, showing two zones of interest.

FIG. 2 is a flow chart of the method of the invention.

FIG. 2 is in the form of a flow chart showing a method of processingpostal packets in order to read a postal address automatically on eachpacket being conveyed through a postal sorting installation to a sortingexit that corresponds to the postal address, the method including a stepof providing assistance by video-coding in the event of it not beingpossible to read the postal address automatically.

Each packet is thus conveyed so as to pass it in front of a camera, andin step 10, the camera takes a digital image of one or more faces of thepacket at a high level of resolution. For a packet of large dimensions,for example a packet in which one of the faces is a rectangle of 1 meter(m) by 80 centimeters (cm), the computer file in which the highresolution image of the packet is stored will be of a size of about 40megabytes, assuming that acquisition is at a resolution of 7 pixels permillimeter (mm) with a gray scale having 256 levels.

In step 20, a processing algorithm is applied to the digital imagecoming from step 10 for the purpose of detecting within said image oneor more zones of interest likely to contain a postal address, and inparticular the destination address for the packet in question. Suchzones of interest can be detected, for example, on the basis ofthresholding applied to the pixels of the digital image, because zonesof interest generally have a background color which defines a kind oflabel in the digital image that is different from the dominantbackground color of the packet. The sorting installation has one or morevideo-coding stations, and if no zone of interest is detectedautomatically in step 20, then the image of the packet is displayed onthe screen of a video-coding station so that the zone of interest can bedefined by a video-coding operator.

In step 30, an automatic address recognition algorithm is applied toeach zone of interest in order to extract a postal address automaticallytherefrom. The outcome of step 30 is successful when only one zone ofinterest is detected in step 20, and when a postal address has beensuitably extracted from said zone of interest in step 30. The outcome ofstep 30 is a failure if no postal address has been extracted from a zoneof interest detected in step 20, for example if the characters are notmachine-readable. The outcome of step 30 is also a failure if aplurality of postal addresses are extracted from a plurality of zones ofinterest and it is not possible automatically to determine which is thepostal address corresponding to the destination. These examples ofoutcomes that lead to failure are not limiting on the method of theinvention.

More particularly, for each zone of interest, analysis can comprise anattempt at extracting one or more strings of characters by opticalcharacter recognition (OCR), followed by analyzing each string ofcharacters in an expert system capable of detecting whether or not astring of characters possesses the characteristics of a postal address.

As shown in FIG. 2, in the event of step 30 being successful, the methodcontinues in step 80 by the packet being conveyed towards a sorting exitthat corresponds to the destination address that has been decoded fromthe image of the packet.

In the event of step 30 failing, each zone of interest detected in step20 is displayed at 40 on the screen of a video-coding station in orderto be processed by a video-coding operator in step 50. If a plurality ofzones of interest are detected during step 20, they can advantageouslybe displayed together on the screen of a video-coding station in step40.

FIG. 1 shows two rectangles R1 and R2 outlining two zones of interest ZIthat have been detected in step 20 on a packet, and these two zones ofinterest are displayed together on the screen in a screen contextbackground F which is representative of the image of the packet obtainedin step 10. The screen background F having one or more zones of interestZI constitutes a meta-image MI in which there can be seen thedestination postal address AD which appears in rectangle R2. In thismeta-image, the context background F which is the image of the face ofthe packet as acquired in step 10, is displayed on the screen at a levelof resolution that is lower than the level of resolution used for thedigital image obtained in step 10, for the purpose of reducing the sizeof the computer files that needs to be transmitted to the video-codingstation so that the time required for transmitting the file can be madecompatible with the rate at which the sorting installation operates. Ina variant, the video-coding station can display the screen background Fat a level of resolution that is matched to the resolution of the screenat the station, enabling each zone of interest to be magnifiedinstantaneously.

As an indication, the level at which the screen background F isdisplayed could be 1 pixel per millimeter, compared with the 7 pixelsper millimeter in the digital image obtained in step 10. The level ofresolution in the zones of interest ZI in the meta-image MI must besufficient to enable the postal address to be read directly from thescreen by the video-coding operator. To further accelerate transmissiontimes, the zones of interest ZI in the meta-image can be displayed onthe screen at an intermediate level of resolution that is higher thanthe level of resolution used for the screen background, but lower thanthe level of resolution in the digital image as obtained at 10. By wayof example, this intermediate level of resolution could be 4 pixels permillimeter.

Consequently, in step 40, the video-coding operator views one or morezones of interest on the screen together with their context on the faceof the packet that appears in the acquired image, thus making itpossible for the operator, for example, to determine which of the zonesof interest contains the destination address. On the basis of thisdisplay, the video-coding operator then acts in step 50 to cause thepostal address to be read semi-automatically.

In step 50, three situations are possible: step 30 might have been ableto decode a plurality of addresses without being able to determineautomatically which is the destination address, or it might not havebeen able to decode any address even through the selected zone is indeedthe zone containing the destination of the packet; step 30 might havefailed to identify any address because the destination address does notappear in the acquired image; or step 30 has not managed to identify anyaddress because the destination address is in the image but lies outsidethe zones of interest as detected in step 20. In the first situation,the operator selects directly on the screen the zone of interest thatcontains the destination address, or the operator inputs the destinationaddress when it appears in a zone of interest that has been selectedautomatically but that has not been read automatically, so that thepacket is then conveyed towards a corresponding sort exit of the sortinginstallation, in step 80. In the second circumstance, the video-codingoperator observes that the destination address does not appear in theimage displayed on the screen of the video-coding station, and thecorresponding packet is sorted manually in step 90. In the thirdcircumstance, the video-coding operator observes that the destinationaddress lies within the image but outside the zones of interest asdetected automatically in step 20, so the operator cancels the zones ofinterest as detected automatically and manually defines the zone ofinterest that contains the destination address and submits this zone tothe algorithm for automatic address recognition in step 60. Thus, step60 can either lead to the packet being sent to a corresponding sortingexit in step 80 if the address is successfully recognized automatically,or else to the packet being sent to other processing 70 in the event ofthe address not being recognized automatically. In step 70, thevideo-coding operator uses the keyboard to manually input thedestination address that appears in the zone of interest as definedduring step 50 but that has not been read automatically in 60, so as tosend the packet to an automatic sorting exit in step 80. If the addressis illegible, then the operator rejects the packet so that it is sent tomanual sorting in step 90.

As can be seen, the method of the invention is particularly applicableto postal packets of large dimensions for which failures of automaticpostal address reading are frequent, given that such packets are oftencovered in stickers, labels, bar codes, etc.

1. A method of processing postal objects, in particular packets, inorder to read a postal address (AD) automatically on each object, themethod including a step of assistance by video-coding, said methodcomprising the following steps for each object: acquiring (10) a digitalimage of the object at a first level of resolution; detecting (20) insaid digital image of the object one or more zones of interest (ZI) ofthe image each apparently containing a postal address; applying anautomatic address recognition algorithm to each detected zone ofinterest in order to extract a postal address (AD) of said object; andif the automatic address recognition step fails, displaying each zone ofinterest (ZI) at a second level of resolution on a screen of avideo-coding station on a screen context background (F) representativeof said digital image of the object in order to enable an operator toperform semi-automatic processing (50) to read the postal address (AD)of said object, wherein the screen context background is displayed onthe screen at a third level of resolution that is lower than said secondlevel of resolution.
 2. The method of claim 1, in which all of the zonesof interest detected in a digital image of an object are displayedtogether on said screen context background if the automatic addressrecognition step fails.
 3. A method according to claim 1, in which saidsecond level of resolution is lower than said first level of resolution.